helper: use generic extra files interface

This replaces the pipes object and integrates context into helper process lifecycle.

Signed-off-by: Ophestra <cat@gensokyo.uk>

helper/direct.go

@@ -1,93 +1,40 @@
 package helper
 
 import (
+	"context"
 	"errors"
 	"io"
-	"os/exec"
 	"sync"
+
+	"git.gensokyo.uk/security/fortify/helper/proc"
 )
 
 // direct wraps *exec.Cmd and manages status and args fd.
 // Args is always 3 and status if set is always 4.
 type direct struct {
-	// helper pipes
-	// cannot be nil
-	p *pipes
-
-	// returns an array of arguments passed directly
-	// to the helper process
-	argF func(argsFD, statFD int) []string
-
 	lock sync.RWMutex
-	*exec.Cmd
+	*helperCmd
 }
 
-func (h *direct) StartNotify(ready chan error) error {
+func (h *direct) Start(ctx context.Context, stat bool) error {
 	h.lock.Lock()
 	defer h.lock.Unlock()
 
 	// Check for doubled Start calls before we defer failure cleanup. If the prior
 	// call to Start succeeded, we don't want to spuriously close its pipes.
-	if h.Cmd.Process != nil {
+	if h.Cmd != nil && h.Cmd.Process != nil {
 		return errors.New("exec: already started")
 	}
 
-	h.p.ready = ready
-	if argsFD, statFD, err := h.p.prepareCmd(h.Cmd); err != nil {
-		return err
-	} else {
-		h.Cmd.Args = append(h.Cmd.Args, h.argF(argsFD, statFD)...)
-	}
-
-	if ready != nil {
-		h.Cmd.Env = append(h.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=1")
-	} else {
-		h.Cmd.Env = append(h.Cmd.Env, FortifyHelper+"=1", FortifyStatus+"=0")
-	}
-
-	if err := h.Cmd.Start(); err != nil {
-		return err
-	}
-	if err := h.p.readyWriteArgs(); err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func (h *direct) Wait() error {
-	h.lock.RLock()
-	defer h.lock.RUnlock()
-
-	if h.Cmd.Process == nil {
-		return errors.New("exec: not started")
-	}
-	defer h.p.mustClosePipes()
-	if h.Cmd.ProcessState != nil {
-		return errors.New("exec: Wait was already called")
-	}
-
-	return h.Cmd.Wait()
-}
-
-func (h *direct) Close() error {
-	return h.p.closeStatus()
-}
-
-func (h *direct) Start() error {
-	return h.StartNotify(nil)
-}
-
-func (h *direct) Unwrap() *exec.Cmd {
-	return h.Cmd
+	args := h.finalise(ctx, stat)
+	h.Cmd.Args = append(h.Cmd.Args, args...)
+	return proc.Fulfill(ctx, h.Cmd, h.files, h.extraFiles)
 }
 
 // New initialises a new direct Helper instance with wt as the null-terminated argument writer.
 // Function argF returns an array of arguments passed directly to the child process.
-func New(wt io.WriterTo, name string, argF func(argsFD, statFD int) []string) Helper {
-	if wt == nil {
-		panic("attempted to create helper with invalid argument writer")
-	}
-
-	return &direct{p: &pipes{args: wt}, argF: argF, Cmd: execCommand(name)}
+func New(wt io.WriterTo, name string, argF func(argsFd, statFd int) []string) Helper {
+	d := new(direct)
+	d.helperCmd = newHelperCmd(d, name, wt, argF, nil)
+	return d
 }